N0.1158, FRESH-WATER CRABS OF AMEBICA—BATHBVN. 509 



PSEUDOTHELPHUSA Saussure. 



Potamia Latrkille, Coufh d'Eutomologie, 1831, p. 338, name jjiooccupiod. Type, 

 ThdphuHa dentata Latrcille. — I)K IIaan, Fauna .Japoii., 1833, p. 23. — Dana, 

 Amor. Jour. Sci., 18r,l, 2d 8or., XII, p. 131; Crust. IJ. S. Hxpl. Exped., 1852,1, 

 p. 293.— Saussuuic, M6m. Soc. Phys. Hist. Nat. Geneve, 18.58, XIV, ji. 435 [19]. 



Boscia Milne-Edwakdh, IliHt. Nat. Crust., 1837, II, p. M, name preoccupiod. 

 Type, Thelphuaa dvntata Latreillo. — Milnk-Ei>waj{D8, Ann. Sci. Nat., 3d Her., 

 Zool., 18.53, XX, p, 207 [173].— A. Milne-Edwakds, Ann. Soc. Entom. France, 

 186f5, 4th H(!r., VI, p. 203. 



Pseudolhelphuea Sauhsuhk, Rev. et Mag. Zool., 1857, 2d ser., IX, p. 305. Typo, P. 

 americana Sauasure. — Smith, Trans. Conn. Acad. Sci., 1870, II, p. 14fi. — 

 Katiiiiun, Proc. II. S. Nat. Mus., 1893, XVI, p. 649. 



Hypolobocera Oktmann, Zool. .Jahrb., Hyst., 1897, X, pp. 298, 323. Type, Potamia 

 clnhnsiH Milno-Edwards and Lucas. 



PotamocarcinuH Outmann, Zool. Jahrb., Syst., 1897, X, pp. 298, 315 (part) ; not 

 Potamocarcinus Milne-Edwards. 



The genus Hypolobocera Ortmann, type and only species, Potamia 

 chUensifi MilneJOd wards and Lucas, founded on the union of the inner 

 suborbitallobe with a projection of tlic front and the consetiuent exclu- 

 sion of the antenna from the orbit, is open to the objection that the 

 distance between the front and the orbital angle is too variable in the 

 n)enibers of a single genus or of a single species in this subfamily to be 

 considered of any importance. In the type specimen of r. chilenms in 

 Philadelphia there is a want of symmetry in the antennae. On both 

 sides the front is united with tlie orbital lobe. On the left side the 

 second of the fixed joints of the antenna is long, and the third joint is 

 attached to the ventral surface of the second, and is very short; it is 

 followed by a fourth, also very short; the liagelluni is absent. On the 

 right side the second joint is shorter than on the left, the following joints 

 are absent, but it is evident that the third joint was never attached as 

 on the left side. In the type' figured by Milne- T^d wards aiid Lucas, 

 which is in the Paris museum, a similar though less striking asymmetry 

 exists. On the left the front t'ouches the inner orbital lobe only by a 

 part of its width, the point of contact forming a sort of ])ridge, for the 

 third article of the antenna appears at the inner angle of the orbital 

 cavity, followed by the fourth, bearing a short llagellum of three arti- 

 cles. On the right side the line of contact of the front and the orbital 

 lo])e is much wider ; only the first two articles of the antenna are i)resent; 

 the second article is much larger than on the opposite side. In P. bou- 

 vieri, a closely allied species, similar variations occur, but in all cases 

 the antenna enters theorbit. The anteinue enter the orbits also in every 

 other species of the Pseudothelphusinje. It is reasonable to infer that 

 the disposition of the single antenna for which the genus Hypolobocera 

 was created is abnormal. 



' Tho antcnual legion of this specimen has been carefully examined by I'rofessor 

 liouvier at my re<£uc;8t. 



